The present application relates generally to communication systems, and more particularly to fabrication of integrated circuit (IC) chips having on-chip transformer-based filters for RF and wireless applications.
Passive filters are typically employed in high frequency (e.g., microwave) communication devices. For example, applications such as high linearity differential amplifiers for CDM (code division multiplexing) and balanced mixers typically require passive filters. These passive filters commonly include coupled line filters. In planar types of coupled line filters, parallel λ/4 transmission lines are often used to provide a transformer function. Due to the length and size of these transmission lines, the coupled line filters are typically fabricated off of integrated circuit (IC) chips in the communication devices.
Integration of filters and other passive elements into communication ICs is often desirable because such integration typically results in reduction of cost and size of communication devices. Therefore, it is desirable to fabricate a passive filter that is suitable for integration on a communication IC chip.